• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.36-36
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• 2017

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.1-5
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• 2016

Capillary barriers, consisting of relatively fine-over-coarse materials, have been suggested as an alternative to traditional compacted soil covers. So, We were analysed to capillary barrier effect according to five cases of multi-layer cover systems. Water balance simulation was conducted with unsaturated flow model HELP to assess unsaturated hydraulic parameters such as hydraulic conductivity, climate affecting the performance of capillary barriers. Simulation were conducted for 5 Cases in the Ulsan area. Result of simulation indicated that three cases was formed unsaturated condition and capillary barrier effect.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.1
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• pp.63-75
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• 2012

This paper gives some basic requirements and preferences of various geological environmental conditions for the final deep geological repository of spent nuclear fuel (SNF). This study also indicates how the requirements and preferences are to be considered prior to the selection of sites for a site investigation as well as the final disposal in Korea. The results of the study are based on the knowledge and experience from the IAEA and NEA/OECD as well as the advanced countries in SNF disposal project. This study discusses and suggests preliminary guideline of the disposal requirements including geological, mechanical, thermal, hydrogeological, chemical and transport properties of host rock with long term geological stabilities which influence the functions of a multi-barrier disposal system. To apply and determine whether requirements and preferences for a given parameter are satisfied at different stages during a site selection and suitability assessment of a final disposal site, the quantitative criteria in each area should be formulated with credibility through relevant research and development efforts for the deep geological environment during the site screening and selection processes as well as specific studies such as productions of safety cases and validation studies using a generic underground research laboratory (URL) in Korea.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.4
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• pp.273-281
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• 2007

Hyperalkaline groundwater formed by groundwater-cement components and its reaction with bedrock in a nuclear waste repository were simulated by geochemical modeling. The result of groundwater-cement components reaction showed that the pH of water was 13.3 and the precipitated minerals were Brucite, Katoite, Calcium Silicate Hydrate(CSH1.1), Ettringite, Hematite, and Portlandite. The result of interaction between such minerals and groundwater sampled in Gyeongju area also showed that the pH of groundwater reached 12.4. Interaction between such hyperalkaline groundwater and granite was simulated by kinetic model during $10^3$ years. This result showed that the final pH of groundwater reached 11.2 and the variation of pH was controlled by dissolution/precipitation of silicate and CSH minerals. Groundwater quality was also determined by dissolution/precipitation of silicate, CSH, oxide minerals. Our results show that geochemical modeling of long-term hyperalkaline groundwater and rock interaction can contribute to the safety assessment of engineered barrier by predicting geochemical condition in repository site.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.4 no.1
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• pp.9-15
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• 2006

For the accurate safety assessment of potential radioactive waste disposal site which is located in the crystalline rock it is important to simulate the mass transportation through engineered and natural barrier system precisely, characterized by porous and fractured media respectively. In this work the methods to construct discrete fracture network for the analysis of flow and mass transport through fractured-porous medium are described. The probability density function is adopted in generating fracture properties for the realistic representation of real fractured rock. In order to investigate the intersection between a porous and a fractured medium described by a 2 dimensional rectangular and a cuboid grid respectively, an additional imaginary fracture is adopted at the face of a porous medium intersected by a fracture. In order to construct large scale flow paths an effective method to find interconnected fractures and algorithms of swift detecting connectivities between fractures or porous medium and fractures are proposed. These methods are expected to contribute to the development of numerical program for the simulation of radioactive nuclide transport through fractured-porous medium from radioactive waste disposal site.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.33-39
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• 2020

A geological repository has been considered as an option for the disposal of high-level radioactive waste (HLW). The HLW is disposed in a host rock at a depth of 500~1,000 meters below the ground surface based on the concept of engineered barrier system (EBS). The EBS is composed of a disposal canister, buffer material, backfill material, and gap-filling material. The compacted bentonite buffer is very important since it can restrain the release of radionuclide and protect the canister from the inflow of ground water. The saturation of the buffer decreases because high temperature in a disposal canister is released into the surrounding buffer material, but saturation of the buffer increases because of the inflow of ground water. The unsaturated properties of the buffer are critical input parameters for the entire safety assessment of the engineered barrier system. In Korea, Gyeongju bentonite can be considered as a candidate buffer material, but there are few test results of the unsaturated properties considering temperature variation. Therefore, this paper conducted experiment of soil-water characteristic curve for the Gyeongju compacted bentonite considering temperature variation under a constant water content condition. The relative error showed approximately 2% between test results and modified van-Genuchten model values.

• Journal of the Mineralogical Society of Korea
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• v.19 no.2 s.48
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• pp.89-98
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• 2006

The thermal conductivities of bentonite blocks with various dry densities (1.6 and $1.8g/cm^3$), water contents (5, 9.4, 15, 20 wt%) and sand contents (0, 10, 20, 30 wt%) were measured in order to investigate the improvement in physical performance of buffer as an engineered barrier. The raw material was domestic bentonite from Oksan mine located in Gyeongju city. The increase in water content was most effective for improving the thermal conductivity. Especiallly, the bentonite blocks with more than 15 wt% of water content showed more than 1.0 W/mK values of thermal conductivity regardless of their dry densities and sand contents. Therefore, if the domestic Oksan bentonite is used as a buffer material, we can suggest that the manufacture of bentonite block having dry density of $1.6g/cm^3$, sand content of $10{\sim}30$ wt% and water content of 15 wt% will be most effective considering the easiness of a manufacturing of bentonite block and the efficiency of an increase in the thermal conductivity.

• The Journal of Engineering Geology
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• v.26 no.2
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• pp.251-260
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• 2016

Groundwater flow due to hydraulic gradients across a geologic barrier surrounding a dam reservoir can cause swamps or wetlands to form on the downstream side of the dam, thereby restricting land use. The difference in head between the reservoir level and the downstream groundwater level creates a hydraulic gradient, allowing water to flow through the geologic barrier. We constructed a drainage system at the Daecheong dam to study the effects on groundwater levels and soil moisture contents. The drainage system consisted of a buried screened pipe spanning a depth of 1-1.5 m below a land surface. Groundwater levels were monitored at several monitoring wells before and after the drainage system was installed. Most well sites recorded a decline in groundwater level on the order of 1 m. The high-elevated site (monitoring well W1) close to the reservoir showed a significant decline in groundwater level of more than 2 m, likely due to rapid discharge by the drainage system. Soil moisture contents were also analyzed and found to have decreased after the installation of the drainage system, even considering standard deviations in the soil moisture contents. We conclude that the drainage system effectively lowered groundwater levels on the downstream side of the dam. Furthermore, we emphasize that water seepage analyses are critical to embankment dam design and construction, especially in areas where downstream land use is of interest.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.529-537
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• 2021

Membrane-type hull and cargo holds have been designed and built for large ship. However, there is a growing interest in applying the same technology to small and medium-sized Liquefied natural gas(LNG) carriers to meet the recent increase in demand for LNG as an ecofriendly fuel and for expanding LNG bunkering infrastructure. The purpose of this study is to apply the IMO Type-B tank to small and medium-sized LNG carriers and verify the safety and suitability of the design. Fatigue crack propagation analysis was performed to install a partial second drip tray installed at the lower part of the LNG cargo tank by calculating the amount of leaked gas in the support structure supporting the cargo tank. First, a program for fatigue crack propagation analysis was developed, in which Paris' law and British Standard 7910 (BS 79110) were applied based on the International Code for the Construction of Equipment and Ships Carrying Liquefied Gases in Bulk, an international standard for LNG carriers. In addition, a surface crack propagation analysis was performed. Next, a methodology for assuming the initial through-crack size was developed to determine the size of the partial second barrier. The analysis was performed for 15 days, which is a possible return time after cracks are detected. Finally, the safety and suitability of the IMO Type-B for LNG cargo tanks required by international regulations were verified. For the accurate analysis of fatigue crack propagation, it is necessary to develop and verify the analysis procedure based on direct analysis and international regulations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.3
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• pp.343-351
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• 2011

Nuclear containment building is the last barrier for being secure from any nuclear power plant accident. Therefore, it is very important to understand the ultimate capacity of nuclear containment building to loads associated with severe accidents. LOCA (loss of coolant accident) is considered as the basic accidental load and CANDU-type containment building is considered as a target structure in order to conduct the numerical analysis for the structural safety of a containment building. The CANDU-type containment building is a prestressed concrete shell structure which has the dome and the cylindrical wall and is reinforced with bonded tendons. In this paper, the evaluation of ultimate internal pressure capacity was carried out by nonlinear analysis of a prestressed concrete containment building using 3-dimensional structural analysis system.